The movie takes place at a high school graduation party, and in a style much like that of the high school movies of the 1980s. The filmmakers were inspired to make the movie because they felt that in most teen films the best scenes were the party scenes. So, they decided to make a movie that was set entirely at a party. Though the film deals in common high school stereotypes, some favor the film's chaotic but appealing mise en scène and performances.

Plot

The film revolves around an eclectic group of students from upstate New York attending a high school graduation party at a large house owned by a rich class member's family. Each character has different plans for the night. Optimistic misfit Preston Myers (Ethan Embry) plans to proclaim his love to his four-year secret crush, to whom he's never had the nerve to speak before, prom queen Amanda Beckett (Jennifer Love Hewitt), who in turn has recently been dumped by her top jock boyfriend, Mike Dexter (Peter Facinelli) who is targeted by classmate William Lichter (Charlie Korsmo), who is plotting revenge against Mike for happily making his high school years a living hell.

Cynical Denise Fleming (Lauren Ambrose) has no intention of going to the party. But when her best friend, Preston, says he's going to proclaim his love for Amanda, she is dragged along. Kenny Fisher (Seth Green) is a ludicrous wannabe rapper who plans on losing his virginity by the end of the night. When he goes into the upstairs bathroom to "get ready", Denise happens to walk in. That is when the pair of former friends learn that the door has a broken doorknob, trapping them in the bathroom. The two begin talking about how they drifted apart, which eventually leads them back to their friendship and escalates into them having sex in the bathroom.

During the course of the party, Amanda deals with being alternately consoled by the drunken girlfriends of Mike's jock friends and her own cousin, and trying to figure out if she truly has an identity past being known as "Mike Dexter's girlfriend". At one point during the night, she discovers a letter with her name written upon it. Unbeknownst to her, the letter was written by Preston, and after reading and subsequently being moved by its contents, she makes it her mission to find him.

Before the party, Mike Dexter convinces his fellow jock friends to follow his lead and dump their girlfriends in order to make a pact in which they all pledge to remain single as they go into college. Later on, an intoxicated Mike learns from a guy named Trip McNeely (Jerry O'Connell in a cameo) a graduate and former stud from his high school that in college, jerks like them are "a dime a dozen" and ironically, find themselves on the receiving end of bullying. This reality is even driven in further by the fact that Trip emphasizes how he dumped his girlfriend in the same fashion that Mike did to score with women which was unsuccessful. Terrified, Mike tries to get Amanda back, but she is happier without him. At the same time, William devises his plan to wreak revenge on Mike by humiliating him. He has his two even more nerdy, X-Files-obsessed friends wait on the roof, while he goes into the party and to drive Mike out. However, while inside the party, William begins drinking in order to fit in. After a while, he drinks enough to make him forget what he was originally doing there and an impromptu sing-along to Guns N' Roses' "Paradise City" causes him to become popular for the evening. William begins talking with Mike, and Mike apologizes for tripping him earlier in the day at the graduation ceremony while William was giving the valedictorian speech. William forgives him, and the two of them seemingly become friends. When Mike and William are jailed as a result of a police bust, Mike takes the blame, saying that he forced William into drinking. However, the next morning when William sees Mike and some of his friends at a local diner, Mike acts as though he remembers nothing of what happened the previous night and proceeds to ridicule him in front of his friends. William, feeling the sting of betrayal, leaves dejected while Mike laughs with his friends to William's chagrin.

Meanwhile, Preston still longs for Amanda, and the scene relocates to a railway station. Amanda visits Preston at the station where she asks him about the letter. Preston confesses he wrote it and that he's about to depart for a pre-college writing workshop with Kurt Vonnegut. But he immediately stops and finally comes back to Amanda where they kiss.

As the film ends, the characters' fates are revealed:

Seven hours later, Preston finally got on a train to Boston. Amanda wrote him a letter for every day that he was away. They are still together.

"Five minutes later Denise dumped Kenny. Ten minutes later they found a bathroom and got back together."

Mike went on to college but, after drinking too much, lost his football scholarship. He ended up forty pounds overweight and working at the car wash, a job he lost when incriminating Polaroids surfaced.

William became one of the most popular students at his school of Harvard. He later went on to open his own computer company that has made him worth millions, and he's dating a supermodel.

William's two nerdy friends were abducted by aliens after discussing that they didn't miss anything by not attending the party.

Another actress whose appearances were deleted was Jennifer Elise Cox. Cox plays a student at the party who is so drunk that her entire dialogue is subtitled to make the viewers understand her slurred speech, and who shows up to explain some problems to each one of the characters, but they cannot understand her. Her scenes, like Amber Benson's, were deleted by the filmmakers at the request of the MPAA prior to the theatrical release to ensure that the movie receive a PG-13 rating because of the drug and alcohol involvement with those scenes.

Several of the actors are well known 'teen movie' actors. Jaime Pressly went on to play Priscilla the Cheerleader in Not Another Teen Movie. Clea DuVall has a cameo in this movie, telling Seth Green "I'm allergic to dancing". She appeared in several teen movies in the '90s, including The Faculty and She's All That (as the suicidal art student). The movie also stars Chris Owen, best known as Sherman from the American Pie movies. He also appeared in She's All That.

Sara Rue (the girl seen cutting up beer ties and calling people sheep) appeared in the TV series Popular alongside Leslie Grossman, who has a cameo as the blonde girl comforting the girl who has been dumped by her boyfriend.

The movie also features a cameo from Jamie Donnelly as Preston's teacher. Donnelly was made famous in 1978's Grease, starring as Pink Lady Jan.